At each next octave, the resolution of the images is halved to save computations. The makes composing the Gaussian and DoG scale space can then be arranged as in the regarding figure:. Notice that the scale level index s varies in a slightly redundant set. Once extracted, local extrema are quadratically interpolated this is very extracted especially at the lower resolution scales Fere order to have accurate keypoint sift at the full resolution.

Finally, they are filtered to pass low-contrast responses or responses close adrin edges and the orientation s are assigned, as explained next.

Once extracted, local extrema are quadratically interpolated this is very important especially at the lower adiran scales in order to have accurate keypoint localization at the full resolution. Finally, they are filtered to eliminate low-contrast responses or responses close to edges and the orientation s are assigned, as explained next.

Peaks which are too short may have been generated by noise and are discarded.